Measuring assembly for detecting faults in a controller

Abstract

The invention relates to a measuring assembly (10) for detecting faults in a controller (1C) having two galvanically isolated voltage domains (3, 5), each voltage domain having a voltage source (4, 6) and different nominal voltages (U1, U2). The measuring assembly comprises an ohmic resistor (Rp) which is connected between the two galvanically isolated voltage domains (3, 5) and connects together the reference potentials of the two voltage sources (4, 6) of the two voltage domains (3, 5); a measuring device (12) which is designed to determine a measurement voltage (UM), produced by a current flow, at the ohmic resistor (Rp); a current source (14) which is designed to generate, in a test mode, a test current (IT) by means of the ohmic resistor (Rp); and an evaluation and control unit (16) which is designed to evaluate the measurement voltage (UM) at the ohmic resistor (Rp) and activate the test mode, the evaluation and control unit (16) additionally being designed to detect, in a normal mode, a short circuit (7) between the two voltage domains (3, 5) and check the functionality of the ohmic resistor (Rp) in the test mode. The invention also relates to a controller (1) having at least one such measuring assembly (10) for detecting faults.

Description

[0001] R. 418034

[0002] - 1 -

[0003] Description

[0004] title

[0005] A measuring arrangement for fault detection in a control unit

[0006] The invention relates to a measuring arrangement for fault detection in a control unit. The present invention also relates to a control unit with such a measuring arrangement for fault detection.

[0007] Modern vehicles increasingly use different voltage domains. As can be seen in Fig. 1, an illustrated embodiment of a control unit 1A of a vehicle, for example, provides a first voltage domain 3 with a first voltage source 4 and a first nominal voltage U1 of 48 volts for high-current consumers V1, and a second voltage domain 5 with a second voltage source 6 and a second nominal voltage U2 of 12 volts for standard consumers V2, V3. Since the cables of these voltage domains 3, 5 can potentially be short-circuited in the vehicle, the standard consumers V2, V3 of the second voltage domain 5 with the second nominal voltage U2 of 12 volts can be destroyed by a short circuit 7 to the first voltage domain 3 with the first nominal voltage U1 of 48 volts. This is illustrated in Fig. 1 by the dashed outline around the standard consumer V2.Since many standard consumers V2, V3 of the second voltage domain 5 with the second nominal voltage U2 of 12 volts would be destroyed by a short circuit 7 to the first voltage domain 3 with the first nominal voltage U1 of 48 volts, the standard consumers V2, V3 of the second voltage domain 5 are protected accordingly. For units with few supply lines, this can be accomplished with little effort. However, for control units that have a large number of lines to the vehicle, such as an airbag control unit, protecting the individual lines is not possible or only with great difficulty. R. 418034.

[0008] - 2 -

[0009] As can be seen in Fig. 2, the standard loads V2, V3 of the second voltage domain 5 can, for example, be galvanically decoupled from the first voltage domain 3 in order to still protect them. This is preferably achieved by an isolated DC / DC converter (not shown) which isolates the second voltage domain 5, with its second nominal voltage U1 of 12 volts, from the first voltage domain 3, with its first nominal voltage U1 of 48 volts. This measure prevents the standard loads V2, V3 of the second voltage domain 5 from being destroyed by a single short circuit 7 to the first voltage domain 3. However, such a short circuit 7 between the two voltage domains 3, 5 can no longer be detected and thus becomes a "latent fault".If another short circuit 7 occurs between the two voltage domains 3, 5, this can again lead to the destruction of a standard consumer V2, V3 of the second voltage domain 5.

[0010] This procedure can also be used if the standard loads V2 and V3 of the second voltage domain 5 are supplied from the first voltage domain 3. In this case, the DC / DC converter, in addition to galvanic isolation, also reduces the voltage to the permissible value.

[0011] From DE 10235 162 A1, a control unit in a vehicle is known which is characterized by the fact that the power supply runs via a converter that provides galvanic isolation. In addition, the component isolated by this galvanic isolation is connected for data exchange with external components and other components in the control unit that are not galvanically isolated by means of a coupling element that also provides galvanic isolation.

[0012] From DE 102015 211 663 A1, an arrangement for use in a motor vehicle is known, comprising at least one central control unit, at least two decentralized control units, and at least two actuators. In this arrangement, at least one signal connection exists between the central control unit and each decentralized control unit. At least one signal connection also exists between each decentralized control unit and each actuator. (R. 418034)

[0013] - 3 -

[0014] The vehicle has a first electrical system and a second electrical system; the first and second electrical systems are galvanically isolated from each other or connected at a star point. The first electrical system includes at least part of the central control unit. The second electrical system includes at least part of the actuators. The second electrical system includes at least part of the decentralized control units.

[0015] Disclosure of the invention

[0016] The measuring arrangement for fault detection in a control unit with the features of independent claim 1 and the control unit for a vehicle with the features of independent claim 13 each have the advantage that a short circuit between two galvanically isolated voltage domains with different nominal voltages can be reliably detected. Furthermore, the functionality of an ohmic resistor, which is connected between two galvanically isolated voltage domains and connects reference potentials of two voltage sources of the two voltage domains, can be monitored in order to detect a short circuit between the two voltage domains.

[0017] If a galvanic isolator is used to decouple a second voltage domain with a lower nominal voltage from a first voltage domain with a higher nominal voltage, the reference potential of the second voltage domain on the secondary side of the galvanic isolator is undefined relative to the reference potential of the first voltage domain (floating potential). Therefore, a single short circuit between terminals of the two galvanically isolated voltage domains can no longer be detected. Each individual short circuit between two terminals of the two voltage domains would thus become a "dormant" or "latent" fault. A second short circuit between two other terminals of the two voltage domains could then lead to the destruction of standard loads in the second voltage domain or to the destruction of the control unit.To solve the problem of not detecting a short circuit between two terminal contacts of the two voltage domains, embodiments of the invention R. 418034 can be used.

[0018] - 4 -

[0019] The reference potentials of the two voltage domains are connected via the ohmic resistor. This provides a high-impedance reference potential against which a standard diagnostic tool can detect a single short circuit. A current flowing through the ohmic resistor in the event of a short circuit allows the corresponding short circuit between the two voltage domains to be detected. Since the ohmic resistor is a crucial component of fault detection, the core of the invention lies in monitoring its functionality. A short circuit in the ohmic resistor would reconnect the two voltage domains galvanically, and a single short circuit could destroy a load or the voltage domain with the lower nominal voltage. If the resistor is interrupted, fault detection would no longer be possible.Furthermore, by monitoring the ohmic resistance, other dormant faults between the voltage domains, such as a short circuit between the reference potentials of the two voltage sources of the two voltage domains, can be detected, which cannot be found via normal fault detection.

[0020] Embodiments of the present invention provide a measuring arrangement for fault detection in a control unit with two galvanically isolated voltage domains, each comprising a voltage source and different nominal voltages. The measuring arrangement comprises an ohmic resistor which is connected between the two galvanically isolated voltage domains and connects the reference potentials of the two voltage sources of the two voltage domains, a measuring device which is configured to determine a test voltage across the ohmic resistor caused by a current flow, a current source which is configured to generate a test current through the ohmic resistor during a test operation, and an evaluation and control unit which is configured to evaluate the test voltage across the ohmic resistor and to activate the test operation.The evaluation and control unit is further designed to detect a short circuit between the two voltage domains during normal operation and to verify the functionality of the ohmic resistance during test operation. R. 418034.

[0021] - 5 -

[0022] Furthermore, a control unit for a vehicle, with two galvanically isolated voltage domains, each comprising a voltage source and different nominal voltages, and a measuring arrangement for fault detection is proposed.

[0023] In this context, the term "control unit" can be understood to mean an electrical device, such as an airbag control unit, which processes or evaluates detected sensor signals.

[0024] In this context, the term "evaluation and control unit" refers to an electrical circuit that is part of a control device and processes or evaluates acquired sensor signals. The evaluation and control unit can have at least one interface, which may be implemented in hardware and / or software. In the case of a hardware-based implementation, the interfaces may, for example, be part of a so-called system ASIC, which incorporates various functions of the evaluation and control unit. However, it is also possible for the interfaces to be separate integrated circuits or at least partially composed of discrete components. In the case of a software-based implementation, the interfaces may be software modules that are, for example, present on a microcontroller alongside other software modules.A computer program product with program code stored on a machine-readable medium such as semiconductor memory, hard disk memory or optical memory, and used to perform the evaluation when the program is executed by the evaluation and control unit, is also advantageous.

[0025] The measures and further developments listed in the dependent claims enable advantageous improvements to the measuring arrangement for fault detection in a control unit specified in independent claim 1 and to the control unit for a vehicle specified in independent claim 13.

[0026] A particular advantage is that the measuring device can be designed as a voltmeter. This allows for simple measurement of the voltage across the ohmic resistor. Furthermore, in the event of a short circuit, a [R. 418034]

[0027] - 6 -

[0028] The corresponding short-circuit current can be determined quickly and easily from the detected voltage increase across the ohmic resistance.

[0029] In an advantageous embodiment of the measuring arrangement, the evaluation and control unit can detect the short circuit between the two voltage domains when the measuring voltage across the ohmic resistor, caused by a short-circuit current, exceeds a first threshold value. The first threshold value can preferably be selected such that it lies between a lower nominal voltage of, for example, 12 volts and a higher nominal voltage of, for example, 48 volts.

[0030] In a further advantageous embodiment of the measuring arrangement, the evaluation and control unit can be further configured to detect the ohmic resistor as faulty during testing if the measured voltage across the resistor, induced by the test current, is below a lower second threshold or above a higher third threshold, which is lower than the first threshold. Alternatively, the ohmic resistor can be detected as fault-free if the measured voltage across the resistor, induced by the test current, is greater than or equal to the second threshold and less than or equal to the third threshold. In this case, the evaluation and control unit can detect a short circuit of the ohmic resistor during testing if the measured voltage across the resistor, induced by the test current, is below the second threshold. In such a short circuit, the measured voltage is 0 volts.Alternatively, the evaluation and control unit can detect an open-circuit resistor during testing if the measurement voltage across the resistor, caused by the test current, exceeds the third threshold. The open-circuit resistor results in a significantly higher measurement voltage than a fault-free resistor, which can be calculated by multiplying the test current value by the resistance value. Accordingly, the second and third thresholds can be selected and predefined.

[0031] In a further advantageous embodiment of the measuring arrangement, the evaluation and control unit can be further designed to initiate the test operation initially, for example when a vehicle is started, or cyclically for a predetermined period of time. R. 418034

[0032] - 7 -

[0033] Activate. The time interval can be set so that a stable voltage measurement across the ohmic resistor is possible.

[0034] In a further advantageous embodiment of the measuring arrangement, the evaluation and control unit can be designed to suspend the test operation if a short circuit between the two voltage domains is detected. This prevents negative influence or damage to the power source.

[0035] In a further advantageous embodiment of the measuring arrangement, the evaluation and control unit can be further configured to generate and output corresponding error messages regarding a detected short circuit between the two voltage domains and / or a malfunction of the ohmic resistor. This allows the driver to be warned in time and contact or visit a workshop.

[0036] In a further advantageous embodiment of the measuring arrangement, the ohmic resistor can provide a high-impedance reference potential. The ohmic resistor can preferably have a value in the range of 1 kilohm to 5 kilohm. Furthermore, the ohmic resistor can limit the short-circuit current and thereby prevent damage to any of the connected devices.

[0037] In a further advantageous embodiment of the measuring arrangement, a capacitor can be connected in parallel to the ohmic resistor, which is designed to reduce EMC interference (EMC: Electromagnetic Compatibility).

[0038] In an advantageous embodiment of the control unit, a first nominal voltage of a first voltage source of a first voltage domain can be higher than a second nominal voltage of a second voltage source of a second voltage domain. For example, the first nominal voltage can be 48 volts, and the second nominal voltage can be 12 volts.

[0039] In a further advantageous embodiment of the control unit, the two voltage domains can be galvanically isolated from each other by an isolation transformer. R. 418034

[0040] - 8 -

[0041] be separated. In this case, the first voltage domain with the higher rated voltage can be connected to a primary side of the isolation transformer, and the second voltage domain with the lower rated voltage can be connected to a secondary side of the isolation transformer.

[0042] An embodiment of the invention is shown in the drawings and is explained in more detail in the following description. In the drawings, identical reference numerals denote components or elements that perform the same or analogous functions.

[0043] Brief description of the drawings

[0044] Fig. 1 shows a schematic representation of a first embodiment of a known control unit with two voltage domains, each comprising a voltage source and different nominal voltages.

[0045] Fig. 2 shows a schematic representation of a second embodiment of a known control unit with two galvanically isolated voltage domains, each comprising a voltage source and different nominal voltages.

[0046] Fig. 3 shows a schematic representation of an embodiment of a control unit according to the invention with two galvanically isolated voltage domains, each comprising a voltage source and different nominal voltages, and an embodiment of a measuring arrangement according to the invention for fault detection in a control unit.

[0047] Embodiments of the invention

[0048] As can be seen from Fig. 3, the illustrated embodiment of a control unit 1 C according to the invention for a vehicle comprises two galvanically isolated voltage domains 3, 5, each comprising a voltage source 4, 6 and different nominal voltages U1, U2, and a measuring arrangement 10 according to the invention for fault detection. R. 418034

[0049] - 9 -

[0050] As can be further seen from Fig. 3, the illustrated embodiment of the measuring arrangement 10 according to the invention for fault detection in a control unit 1 C comprises an ohmic resistor Rp, which is connected between the two galvanically isolated voltage domains 3, 5 and connects reference potentials of the two voltage sources 4, 6 of the two galvanic voltage domains 3, 5, a measuring device 12, which is designed to determine a measuring voltage UM across the ohmic resistor Rp caused by a current flow, a current source 14, which is designed to generate a test current IT through the ohmic resistor Rp in a test operation, and an evaluation and control unit 16, which is designed to evaluate the measuring voltage UM across the ohmic resistor Rp and to activate the test operation.In this case, the evaluation and control unit 16 is further designed to detect a short circuit 7 between the two voltage domains 3, 5 in normal operation and to check the functionality of the ohmic resistance Rp in test operation.

[0051] In the illustrated embodiment of the control unit 1 C, a first voltage source 4 of a first voltage domain 3 has a first nominal voltage U1 of 48 volts, which is higher than a second nominal voltage U2 of 12 volts of a second voltage source 6 of a second voltage domain 5. Furthermore, the two voltage domains 3 and 5 are galvanically isolated from each other by an isolation transformer (not shown in detail).

[0052] As can be further seen from Fig. 3, the measuring device 12 in the illustrated embodiment of the measuring arrangement 10 is designed as a voltage measuring device V and detects the measuring voltage UM. The evaluation and control unit 16 detects the short circuit 7 between the two voltage domains 3, 5 when the measuring voltage UM caused by a short-circuit current Ik exceeds a first threshold value across the ohmic resistor Rp, which is predefined, for example, in the range of 15 volts to 20 volts.

[0053] In the illustrated embodiment of the measuring arrangement 10, the evaluation and control unit 16 is further designed to detect the ohmic resistance Rp as faulty during test operation if the measuring voltage UM across the ohmic resistance Rp, caused by the test current IT, is below a smaller second R. 418034

[0054] - 10 -

[0055] The resistance Rp is recognized as fault-free if the measurement voltage UM across the resistance Rp, caused by the test current IT, is greater than or equal to the second threshold and less than or equal to the third threshold. In the illustrated embodiment, the resistance Rp is recognized as fault-free if the measurement voltage UM across the resistance Rp is in the range between 1 volt and 9 volts. In this case, the evaluation and control unit 16 detects a short circuit 7 of the resistance Rp during test operation if the measurement voltage UM across the resistance Rp, caused by the test current IT, is below the second threshold.Alternatively, in test mode, the evaluation and control unit 16 detects an open ohmic resistance Rp if the measurement voltage UM caused by the test current IT across the ohmic resistance Rp is above the third threshold value.

[0056] In the illustrated embodiment of the measuring arrangement 10, the evaluation and control unit 16 is further configured to activate the test operation initially or cyclically for a predetermined time period. Furthermore, the evaluation and control unit 16 is configured to suspend the test operation if a short circuit 7 between the two voltage domains 3, 5 is detected.

[0057] In the illustrated embodiment of the measuring arrangement 10, the evaluation and control unit 16 is further designed to generate and output corresponding error messages about a detected short circuit 7 between the two voltage domains 3, 5 and / or about a lack of functionality of the ohmic resistance Rp.

[0058] In the illustrated embodiment of the measuring arrangement 10, the ohmic resistor Rp provides a high-impedance reference potential. For this purpose, the ohmic resistor Rp has a value in the range of 1 kilohm to 5 kilohm. Furthermore, the ohmic resistor Rp limits the short-circuit current Ik.R. 418034

[0059] - 11 -

[0060] As can be seen from Fig. 3, a capacitor Cp is connected in parallel to the ohmic resistor Rp and designed to reduce EMC interference.

Claims

R. 418034 - 12 - Claims 1. Measuring arrangement (10) for fault detection in a control unit (1 C) with two galvanically isolated voltage domains (3, 5), each comprising a voltage source (4, 6) and different nominal voltages (U1, U2), comprising an ohmic resistor (Rp) which is connected between the two galvanically isolated voltage domains (3, 5) and connects the reference potentials of the two voltage sources (4, 6) of the two voltage domains (3, 5), a measuring device (12) which is configured to determine a measuring voltage (UM) across the ohmic resistor (Rp) caused by a current flow, a current source (14) which is configured to generate a test current (IT) through the ohmic resistor (Rp) in a test operation, and an evaluation and control unit (16) which is configured to evaluate the measuring voltage (UM) across the ohmic resistor (Rp) and to activate the test operation, wherein the evaluation and control unit (16) is further explained,to detect a short circuit (7) between the two voltage domains (3, 5) during normal operation and to check the functionality of the ohmic resistance (Rp) during test operation.

2. Measuring arrangement (10) according to claim 1, characterized in that the measuring device (12) is designed as a voltage measuring device (V).

3. Measuring arrangement (10) according to claim 1 or 2, characterized in that the evaluation and control unit (16) detects the short circuit (7) between the two voltage domains (3, 5) when the measuring voltage (UM) caused by a short-circuit current (Ik) at the ohmic resistance (Rp) exceeds a first threshold value.

4. Measuring arrangement (10) according to one of claims 1 to 3, characterized in that the evaluation and control unit (16) further R. 418034 - 13 - The device is designed to recognize the ohmic resistance (Rp) as faulty during test operation if the measurement voltage (UM) across the ohmic resistance (Rp) caused by the test current (IT) is below a smaller second threshold or above a larger third threshold which is smaller than the first threshold, or to recognize the ohmic resistance (Rp) as fault-free if the measurement voltage (UM) across the ohmic resistance (Rp) caused by the test current (IT) is greater than or equal to the second threshold and less than or equal to the third threshold.

5. Measuring arrangement (10) according to claim 4, characterized in that the evaluation and control unit (16) detects a short circuit of the ohmic resistance (Rp) during test operation if the measuring voltage (UM) caused by the test current (IT) across the ohmic resistance (Rp) is below the second threshold value.

6. Measuring arrangement (10) according to claim 4 or 5, characterized in that the evaluation and control unit (16) detects an open ohmic resistance (Rp) during test operation when the measuring voltage (UM) across the ohmic resistance (Rp) caused by the test current (IT) is above the third threshold value.

7. Measuring arrangement (10) according to one of claims 1 to 6, characterized in that the evaluation and control unit (16) is further designed to activate the test operation initially or cyclically for a predetermined period of time.

8. Measuring arrangement (10) according to one of claims 1 to 7, characterized in that the evaluation and control unit (16) is further designed to suspend the test operation if a short circuit (7) between the two voltage domains (3, 5) is detected.

9. Measuring arrangement (10) according to one of claims 1 to 8, characterized in that the evaluation and control unit (16) is further designed to send corresponding error messages about a detected R. 418034 - 14 - to generate and output a short circuit (7) between the two voltage domains (3, 5) and / or a lack of functionality of the ohmic resistance (Rp).

10. Measuring arrangement (10) according to one of claims 1 to 7, characterized in that the ohmic resistance (Rp) provides a high-impedance reference potential and has a value in the range of 1 kiloohm to 5 kiloohm.

11. Measuring arrangement (10) according to one of claims 1 to 10, characterized in that the ohmic resistance (Rp) limits the occurring short-circuit current (Ik).

12. Measuring arrangement (10) according to one of claims 1 to 11 , characterized in that a capacitor (Cp) is connected in parallel to the ohmic resistor (Rp) which is designed to reduce EMC interference.

13. Control unit (1 C) for a vehicle, comprising two galvanically isolated voltage domains (3, 5), each comprising a voltage source (4, 6) and different nominal voltages (U1, U2), and a measuring arrangement (10) for fault detection, which is designed according to one of claims 1 to 12.

14. Control unit (1) according to claim 13, characterized in that a first nominal voltage (U1) of a first voltage source (4) of a first voltage domain (3) is higher than a second nominal voltage (U2) of a second voltage source (6) of a second voltage domain (5).

15. Control unit (1) according to claim 13 or 14, characterized in that the two voltage domains (3, 5) are galvanically isolated from each other by a transformer.

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